The present invention relates generally to brakes for motor vehicles, particularly to an electric caliper for a brake system in a motor vehicle.
A brake system for a motor vehicle, and in particular an automotive vehicle, functionally reduces the speed of the vehicle or maintains the vehicle in a rest position. Various types of brake systems are commonly used in automotive vehicles, including hydraulic, anti-lock or xe2x80x9cABS,xe2x80x9d and electric or xe2x80x9cbrake by wire.xe2x80x9d For example, in a hydraulic brake system, the hydraulic fluid transfers energy from a brake pedal to a brake pad for slowing down or stopping rotation of a wheel of the vehicle. Electronics control the hydraulic fluid in the hydraulic brake system. In the electric brake system, the hydraulic fluid is eliminated. Instead, the application and release of the brake pad is controlled by an electric caliper.
Generally, the electric caliper includes a motor and a gear system. Typically, either a few large gears or many small gears for the gear system are needed to achieve the necessary load transfer. Also, the geometry of the motor influences its efficiency, since the preferred shape is long and thin. However, there is a limited amount of space available in the wheel for packaging the type of gears or motor necessary to obtain the same load transfer as in the hydraulic brake system. Therefore, space limitations constrain the use of an electric caliper in an automotive vehicle.
The present invention is a brake caliper comprising a motor having a shaft, at least one first planetary gear, and at least one second planetary gear. The at least one first planetary gear is rotatably engaged with the shaft and with a piston, and is operatively engaged with a first carrier. The at least one second planetary gear is operatively engaged with the first stage carrier and with a second carrier. A ball screw is engaged with the second stage carrier for rotation therewith, and a ball screw nut is operatively engaged with the ball screw. A parking brake for the caliper is also provided.
Accordingly, it is an object of the present invention to provide a caliper of the type described above with a large diameter piston and a shorter package length.
Another object of the present invention is to provide a caliper of the type described above including a motor that can be packaged inside of the ball screw.
Still another object of the present invention is to provide a caliper of the type described above in which the electronics are disposed at a distance from the rotor.
Still another object of the present invention is to provide a caliper of the type described above having a park brake feature.
These and other features and advantages of the invention will become further apparent from the following detailed description of the presently preferred embodiments, read in conjunction with the accompanying drawings. The detailed description and drawings are merely illustrative of the invention rather than limiting, the scope of the invention being defined by the appended claims and equivalents thereof.